JDK 9 Outreach (DRAFT)

Introduction

With JDK 9 development underway in the OpenJDK Community, and based on our experiences with open source projects testing against JDK 9 Early Access builds in the Quality Outreach effort, it seems like a good idea to compile the accumulated wisdom to make it easier for new projects to start testing against JDK 9.

Caveat Lector

JDK 9 has not been released yet. That means the tips and suggestions accumulated here should not be taken as the final word on how to adjust your code for JDK 9 as some things may (and probably will) change as the set of JEPs targeted for JDK 9 changes. If in doubt, ask - preferably on the adoption-discuss mailing list.

The Little Things

Before you get started testing your code against JDK 9, there are a few little things to consider.

JDK 9 Builds

You can build JDK 9 yourself by following the build instructions to build the OpenJDK source code in the jdk9/jdk9 forest. Please check the list of supported build platforms to verify that your build platform is supported before you attempt building JDK 9 from source yourself.

JDK 9 Early Access builds might also be provided by third parties. Oracle publishes regular JDK 9 builds at http://jdk9.java.net, for example.

Unrecognized VM options

If your application's startup script launches the JDK 9 JVM with an unrecognized VM option, it will exit and let you know that it couldn't create a VM because of that unrecognized VM option. Some of the VM flags that were deprecated in JDK 8, like those relating to the permanent generation, which was removed in JDK 8, have been removed in JDK 9.